Internal combustion engine with wind exhaust duct and vehicle mounted with internal combustion engine

ABSTRACT

To increase the wind volume of the cooling wind flowing through a radiator and to enhance the cooling performance of the radiator by providing a wind exhaust duct using a crankcase of an internal combustion engine. A cooling device of the internal combustion engine includes a radiator arranged lateral to crankcases. A wind exhaust duct exhausts the cooling wind passed through the radiator to the atmosphere. The wind exhaust duct is extends along a rotational axis of the crankshaft at the upper portion of the crankcases and the upper portion of the transmission case.

CROSS-REFERENCE TO RELATED APPLICATIONS

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application Nos. 2006-254952 and 2007-162947, filed in Japanon Sep. 20, 2006 and Jun. 20, 2007, respectively. The entirety of eachof the above applications is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an internal combustion engine thatincludes an engine main body configured by a crankcase and a coolingdevice equipped with a radiator cooled by cooling wind. The presentinvention also relates to a vehicle on which the internal combustionengine is mounted.

2. Background of the Invention

A cooling device of an internal combustion engine that includes aradiator cooled by the cooling wind is known from, for example, JP-A No.2002-129960. In this known cooling device, a wind outlet portion forexhausting cooling wind that has passed through the radiator to theatmosphere is formed in a cylindrical shroud, coupled to the crankcase,for holding the radiator.

In order to enhance the cooling performance of the cooling water fromthe radiator, a radiator core of the radiator may be enlarged or acooling fan may be enlarged to increase the wind volume of the coolingwind that passes through the radiator. However, this leads to anenlargement of the radiator and an enlargement of the cooling fan. Thus,consideration is made in increasing a passage area of the wind outletportion formed in the shroud as a means for increasing the wind volumeof the cooling wind. However, the shroud has limitations in terms ofensuring the rigidity of the shroud to support the radiator and anincrease in the passage area of the wind outlet portion also haslimitations. Thus, the increase in the wind volume of the cooling windis also limited. Furthermore, when the internal combustion engine is astationary type or when the vehicle mounted with the internal combustionengine is stopped, the cooling wind exhausted from the wind outletportion close to the radiator sometimes again flows into the radiator,thereby lowering the cooling performance of the radiator.

In a vehicle mounted with an internal combustion engine, such as avehicle in which the internal combustion is supported in a swingingmanner by a vehicle body integrally with the wheels, enhancement of thecooling performance of the radiator by traveling wind cannot be expectedtoo much when the radiator is arranged lateral to the engine main body,since the traveling wind is less likely to flow into the radiator. Thus,the wind volume of the cooling wind must be increased in order toenhance the cooling performance of the radiator.

Moreover, in a vehicle mounted with an internal combustion engine, thewind exhaust duct is sometimes preferably arranged so as to extend inthe front and back direction instead of being arranged so as to extendin the left and right direction due to mounting modes of the internalcombustion engine with respect to the vehicle body when increasing thewind volume of the cooling wind by exhausting the cooling wind (i.e.,exhausted wind) passed through the radiator through the wind exhaustduct. In this case, however, the wind exhaust outlet portion of the windexhaust duct becomes close to a fender that covers the wheels, and thefender sometimes inhibits smooth exhaust of the exhausted wind from thewind exhaust outlet portion. When the wind exhaust duct is arrangedavoiding the fender, the wind exhaust duct enlarges, and furthermore, acompact arrangement becomes difficult.

SUMMARY OF THE INVENTION

The preset invention is proposed in view of the above to increase thewind volume of the cooling wind that flows through the radiator and toenhance the cooling performance of the radiator by arranging the windexhaust duct using a crankcase of the internal combustion engine. Thepresent invention also aims to enhance the cooling performance of theradiator in a vehicle mounted with the internal combustion engineequipped with the radiator, which is arranged lateral to the engine mainbody. The present invention also aims to prevent smooth exhaust of theexhausted wind from being inhibited by the fender and to miniaturize thewind exhaust duct and achieve a compact arrangement by exhausting theexhausted wind of the wind exhaust duct through the fender to a spaceformed between the wheels and the fender. The present invention furtheraims to smooth the flow of the exhausted wind in the wind exhaust ductby suppressing entrance of foreign materials such as small rocks intothe wind exhaust duct. The present invention also aims to enhance thecooling effect of the crankcase with the exhausted wind exhausted fromthe wind exhaust duct. The present invention further aims to promoteexhaust of the exhausted wind using airflow generated by the rotation ofthe wheels.

A first aspect of the present invention relates to an internalcombustion engine having an engine main body configured by a crankcaseand a cooling device including a radiator arranged lateral to the enginemain body, wherein the cooling device includes a wind exhaust duct forexhausting exhausted wind, which is cooling wind passed through theradiator, to an atmosphere, and the wind exhaust duct is arranged on anupper portion of the crankcase.

According to a second aspect of the present invention, a powertransmission system including a transmission case for accommodating atransmission is arranged on the side opposite to the radiator with thecrankcase in between in a direction of a rotational axis of a crankshaftsupported by the crankcase, and the wind exhaust duct is extended alongthe rotational axis of the crankshaft and position on the upper portionof the transmission case in the internal combustion engine.

According to a third aspect of the present invention, the internalcombustion engine is supported by a body frame at supporting partsarranged at a lower portion of the crankcase.

A fourth aspect of the present invention relates to a vehicle withwheels, the vehicle having an internal combustion engine mountedthereon, the internal combustion engine having an engine main bodyconfigured by a crankcase and a cooling device including a radiatorarranged lateral to the engine main body, wherein the cooling deviceincludes a wind exhaust duct for exhausting exhausted wind, which iscooling wind passed through the radiator, from an wind exhaust outletportion to an atmosphere, and the wind exhaust duct is arranged on anupper portion of the crankcase.

According to a fifth aspect of the present invention, a fender forcovering the wheel from an outer side in a radial direction having arotational axis of the wheel as a center is further arranged, whereinthe exhausted wind is exhausted to a space formed between the wheel onan inner side in the radial direction and the fender using an openingformed in the fender in the vehicle.

According to a sixth aspect of the present invention, a fender forcovering the wheel from an outer side in a radial direction having arotational axis of the wheel as a center is further arranged, whereinthe wind exhaust duct is coupled with the fender, and the wind exhaustoutlet portion is formed by a coupling portion to the fender of the windexhaust duct in the vehicle.

According to a seventh aspect of the present invention, the wind exhaustoutlet portion opens at a position facing a tread of the wheel in theradial direction, and a shielding part for suppressing foreign materialstaken up by the wheel or foreign materials attached to the tread andscattered by centrifugal force from entering inside the wind exhaustduct is arranged in the wind exhaust duct or the fender in the vehicle.

According to the eighth aspect of the present invention, the shieldingpart extends along an outer surface of the crankcase in the vehicle.

According to the ninth aspect of the present invention, the exhaustedwind is exhausted from the wind exhaust outlet portion to a space formedbetween the wheel and the fender or to a space formed between the wheeland the crankcase in a direction of a rotating direction at a regionclosest to the wind exhaust outlet portion in the wheel in the vehicle.

According to the first aspect of the present invention, limitationsrelated to the size of the passage area of the wind exhaust duct aresmall and the wind volume of the cooling wind that passes through theradiator can be increased by increasing the passage area of the windexhaust duct since the wind exhaust duct is arranged using the upperportion of the crankcase, whereby the cooling performance of theradiator, and furthermore, the internal combustion engine is enhanced.

According to the second aspect of the present invention, the coolingwind exhausted to the atmosphere is prevented from again passing throughthe radiator since the wind exhaust duct is extended to the sideopposite to the radiator with the crankcase in between, whereby thecooling performance of the radiator is enhanced.

According to the third aspect of the present invention, the supportingparts for supporting the internal combustion engine are not arranged atthe upper portion of the crankcase. Therefore, the passage area of thewind exhaust duct to be arranged at the upper portion of the crankcasecan be enlarged thereby increasing the wind volume of the cooling wind,whereby the cooling performance of the radiator is enhanced and thedegree of freedom of layout of the wind exhaust duct is increased.

According to the fourth aspect of the present invention, limitationsrelated to the size of the passage area of the wind exhaust duct aresmall and the wind volume of the cooling wind that passes through theradiator can be increased by increasing the passage area of the windexhaust duct since the wind exhaust duct is arranged using the upperportion of the crankcase even in the case of the vehicle mounted withthe internal combustion engine, in which vehicle enhancement of thecooling performance of the radiator by traveling wind cannot be expectedtoo much since the radiator is arranged lateral to the engine main body,whereby the cooling performance of the radiator, and furthermore, theinternal combustion engine is enhanced.

According to the fifth aspect of the present invention, the exhaustedwind of the wind exhaust duct is exhausted to the space formed betweenthe wheel and the fender using the opening formed in the fender.Therefore, the exhausted wind from the wind exhaust outlet portion isprevented from hitting the fender and inhibiting the exhaust of theexhausted wind, and furthermore, the wind exhaust duct can beminiaturized and compact arrangement can be achieved since the windexhaust duct does not need to be arranged avoiding the fender.

According to the sixth aspect of the present invention, the exhaustedwind of the wind exhaust duct is discharged to the space formed betweenthe wheel and the fender through the wind exhaust outlet portion or theopening formed in the fender since the wind exhaust outlet portion ofthe wind exhaust duct is formed by the coupling portion to the fender ofthe wind exhaust duct, whereby the exhausted wind from the wind exhaustoutlet portion is prevented from hitting the fender and inhibiting theexhaust of the exhausted wind, and furthermore, the wind exhaust ductcan be miniaturized and compact arrangement can be achieved since theexhaust wind duct does not need to be arranged avoiding the fender.

According to the seventh aspect of the present invention, the exhaust ofthe exhausted wind from the wind exhaust outlet portion is prevented orsuppressed from being inhibited by foreign materials by the shieldingpart, whereby the flow of the exhausted wind in the wind exhaust ductincluding the wind exhaust outlet portion becomes smooth, whichcontributes to enhancing the cooling performance of the radiator.

According to the eighth aspect of the present invention, the exhaustedwind exhausted from the wind exhaust duct flows along the outer surfaceof the crankcase. Therefore, the contacting range of the outer surfaceand the exhausted wind increases, thereby enhancing the cooling effectof the crankcase by the exhausted wind.

According to the ninth aspect of the present invention, air flow in thedirection substantially the same as the exhausting direction of theexhausted wind is generated by the rotation of the wheels in the spacebetween the wheel and the fender or the space between the wheel and thecrankcase to which the exhausted wind is exhausted. Therefore, theexhaust of the exhausted wind from the wind exhaust outlet portion ispromoted by using such airflow, thereby increasing the wind volume ofthe cooling wind that passes through the radiator and enhancing thecooling performance of the radiator.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention, and wherein:

FIG. 1 is a left side view of a first embodiment of the presentinvention showing a motorcycle mounted with a power unit including awater cooled internal combustion engine and a power transmission system;

FIG. 2 is a perspective view of the main parts of the power unit of FIG.1;

FIG. 3 is a cross sectional view of the main parts having a planeincluding the cylinder axis of the internal combustion engine of FIG. 1and being parallel to the rotational axis of the crankshaft as the maincross section;

FIG. 4 is a right side view of the main parts of the internal combustionengine of FIG. 1;

FIG. 5 is a cross sectional view of the main parts taken along line V-Vof FIG. 3;

FIG. 6 is a view of a second embodiment of the present invention,corresponding to FIG. 1, showing a motorcycle mounted with a power unitincluding a water cooled internal combustion engine and a powertransmission system;

FIG. 7 is a perspective view of the main parts of the power unit and afender of the motorcycle of FIG. 6;

FIG. 8 is a rear view of the main parts of the motorcycle of FIG. 6;

FIG. 9 is a cross sectional view of the main parts taken along lineIX-IX of FIG. 8; and

FIG. 10 is a view of a third embodiment of the present invention,corresponding to FIG. 1, showing a motorcycle mounted with a power unitincluding a water cooled internal combustion engine and a powertransmission system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference tothe accompanying drawings, wherein the same reference numerals will beused to identify the same or similar elements throughout the severalviews. It should be noted that the drawings should be viewed in thedirection of orientation of the reference numerals.

FIGS. 1 to 5 are views describing the first embodiment. With referenceto FIG. 1, a scooter type motorcycle 1 is a compact vehicle that servesas a vehicle mounted with a water-cooled internal combustion engine Eapplied with the present invention. The scooter type motorcycle 1includes: a vehicle body configured by a body frame F; a vehicle bodycover C made of synthetic resin for covering the body frame F; and afront wheel 9 and a rear wheel 10 serving as wheels. The body frame Fincludes: a head pipe 2 positioned at the front end of the vehicle body;one down tube 3 extending diagonally downward towards the rear from thehead pipe 2; a pair of left and right rear frames 4 connected to ahorizontal portion 3 a in the lower portion of the down tube 3 andextending diagonally upward towards the rear from both left and rightsides of the horizontal portion 3 a; and a plurality of cross members(not shown) for connecting the left and right rear frames 4. The compactvehicle includes three-wheeled vehicles in addition to motorcycles, andalso includes saddle-ride type vehicles.

In the specification, the directions up and down refer to the verticaldirection. Furthermore, in the embodiment, front and rear, left andright correspond to front and rear, left and right of the motorcycle 1,where front or rear is one or the other in the direction of a cylinderaxis, and right or left is one or the other in the direction of arotational axis Le of a crankshaft 26 or in the vehicle width direction.

A steering handlebar 7 is arranged on the upper end and a front fork 8on the lower end of a steering shaft 6 rotatably supported by the headpipe 2. The front wheel 9 is journaled to the lower end of the frontfork 8. The rear wheel 10 serving as a driving wheel is journaled to therear end of a power unit P for generating power to rotatably drive therear wheel 10. The power unit P has the front end thereof supported in aswinging manner with a pair of brackets 18 a, 18 b (see also FIG. 3)serving as supporting parts arranged at the lower portion of thecrankcase 23, to be hereinafter described, at a pivot shaft 13 supportedby way of a link 12 to a support plate 11 coupled to the front portionof the pair of rear frames 4, and the rear end supported at the rearportion of the left rear frame 4 by way of a rear suspension 14. Thus,the power unit P and the rear wheel 10 are supported by the body frame Fso as to swing in the up and down direction by way of the supportingplate 11, the link 12, and the pivot shaft 13. Therefore, the internalcombustion engine E and the power transmission system T configuring thepower unit P, and furthermore, a cooling device 50 including a radiator52 and a cooling fan 53 arranged in the internal combustion engine E aresupported by the body frame F in a swinging manner integrally with therear wheel 10 that is supported by the body frame F in a swingingmanner.

In addition, a cylindrical mount rubber 19 serving as a buffer isinterposed between the pivot shaft and the brackets 18 a, 18 b (see FIG.4, FIG. 5).

Referring also to FIGS. 2 and 3, the power unit P supported by the bodyframe F and arranged at the left portion of the body frame F includes alaterally mounted one-cylinder 4-stroke internal combustion engine Ehaving the rotational axis Le in which the crankshaft 26 is directed inthe vehicle width direction (left and right direction), and a powertransmission system T for transmitting power generated by the internalcombustion engine E to the rear wheel 10. The power transmission systemT includes a belted transmission 15 serving as a transmission, atransmission case 16 for accommodating the transmission 15, and a finalreduction mechanism (not shown) configured by gear trains. Thetransmission 15 that is accommodated in a power transmission chamber 17formed by the transmission case 16 includes: a drive pulley 15 barranged on a drive shaft 15 a integrally formed coaxially with thecrankshaft 26 and rotatably driven by the crankshaft 26; a driven pulley(not shown) arranged on an output shaft coupled to the rear wheel 10 byway of the final reduction mechanism; and a V-belt 15 c stretched acrossthe drive pulley 15 b and the driven pulley. The gear ratio of thetransmission 15 is automatically changed when the effective radius ofthe driven pulley is changed at the same time as when the effectiveradius of the drive pulley 15 b is changed by a centrifugal weight 15 dthat moves according to the rotation speed of the engine. Thetransmission case 16 is configured by a case body 16 a and atransmission cover 16 b coupled to the left end of the case body 16 awith a great number of bolts.

With reference to FIGS. 1 to 5, the internal combustion engine Eincludes: an engine main body (hereinafter referred to as “engine mainbody”) configured by a cylinder block 20 made up of one cylinder 20 aformed with a cylinder bore 20 b to which a piston 24 is fitted in areciprocating manner; a cylinder head 21 coupled to the front end of thecylinder block 20; a head cover 22 coupled to the front end of thecylinder head 21; and a crankcase 23 coupled to the rear end of thecylinder block 20. The cylinder 20 a is arranged on the body frame F ina state tilted slightly upward with respect to the horizontal surface,and thus in a state greatly tilted forward so that the cylinder axis Lythereof extends slightly diagonally upward towards the front.

The crankcase 23 is formed integrally with the case body 16 a, and isdivided into a left half case 23 a formed integrally with the bracket 18a and a right half case 23 b formed integrally with the bracket 18 b.The bracket 18 a is integrally molded with the case body 16 a since thecase body 16 a is integrally molded with the left half case 23 a. Thecrankshaft 26 coupled to the piston 24 by way of a connecting rod 25 isaccommodated in a crank chamber 27 formed by the crankcase 23 and isrotatably supported by both half cases 23 a, 23 b by way of a pair ofmain bearings 28.

The left axial end portion of the crankshaft 26 projecting towards theleft from the crank chamber 27 extends into the power transmissionchamber 17 and forms the drive shaft 15 a. The right axial end portionof the crankshaft 26 projecting towards the right from the crank chamber27 extends into an auxiliary chamber 30 in which an AC generator 31 anda cooling fan 53 are accommodated and forms a drive shaft 29 of the ACgenerator 31 and the cooling fan 53. Thus, the drive shaft 29 isintegrally formed coaxially with the crankshaft 26 and rotatably drivenby the crankshaft 26. The auxiliary chamber 30 is formed by the rightend portion 23 e of the right half case 23 b and the cylindrical shroud54 coupled to the right end portion 23 e.

With reference to FIGS. 3 and 5, the cylinder head 21 is formed with acombustion chamber 35 including a concave portion at a position facingthe cylinder bore 20 b in the direction of the cylinder axis, an intakeport 36 and an exhaust port 37 opening to the combustion chamber 35, anda spark plug 38 facing the combustion chamber 35. In a valve trainchamber 39 formed by the cylinder head 21 and the head cover 22, a valvetrain 40 for driving to open and close an intake valve 41 for openingand closing the intake port 36 and an exhaust valve 42 for opening andclosing the exhaust port 37 are accommodated. The valve train 40 ofoverhead camshaft type includes a camshaft 40 a formed with an intakecam 40 a 1 and an exhaust cam 40 a 2 and rotatably arranged in thecylinder head 21 serving as valve operating cams, an intake rocker arm40 c and an exhaust rocker arm 40 d supported in a swinging manner by arocker shaft 40 b and respectively driven and swung by the intake cam 40a 1 and the exhaust cam 40 a 2. The camshaft 40 a having a rotationalaxis La parallel to the rotational axis Le is coupled to the crankshaft26 by way of a winding power transmission mechanism 43, and is rotatablydriven by the power of the crankshaft 26 at ½ the rotation speedthereof.

The power transmission mechanism 43 accommodated in a chain chamber 44serving as an accommodating chamber arranged along the cylinder axis Lyat the right end portion 23 e of the crankcase 23, the right end portion20 e of the cylinder block 20, and the right end portion 21 e of thecylinder head 21 includes a drive sprocket 43 a serving as a drive bodyarranged in the crankshaft 26, a cam sprocket 43 b serving as a drivenbody arranged in the camshaft 40 a, and an endless chain 43 c serving asan endless power transmission band stretched over both sprockets 43 a,43 b. The intake cam 40 a 1 and the exhaust cam 40 a 2 of the rotatingcamshaft 40 a open/close operate the intake valve 41 and the exhaustvalve 42 at a predetermined timing in synchronization with the rotationof the crankshaft 26 through the intake rocker arm 40 c and the exhaustrocker arm 40 d.

With reference to FIG. 1, the internal combustion engine E includes: anintake device 45 with an air cleaner 45 a, a throttle valve device 45 b,and an intake pipe 45 c connected to a connection portion 21 i of thecylinder head 21, for guiding the intake air to the combustion chamber35; a fuel injection valve 47 attached to the intake pipe 45 c forsupplying the fuel to the intake air; and an exhaust device 46 includingan exhaust pipe 46 a and a silencer 46 b for guiding the exhaust gasflowed out from the exhaust port 37 to the outside of the internalcombustion engine E, and also includes a cooling device 50 for flowingthe cooling water for cooling the cylinder block 20 and the cylinderhead 21 to water jackets Jb, Jh arranged at the cylinder block 20 andthe cylinder head 21, with reference also to FIGS. 2 to 5.

The intake air that flows through the intake device 45 isflow-rate-controlled by the throttle valve 45 b 1 arranged in thethrottle valve device 45 b, and mixed with fuel supplied from the fuelinjection valve 47 to generate fuel-air mixture. The fuel-air mixtureflows into the combustion chamber 35 through the intake port 36 when theintake valve 41 is opened, and then ignited and combusted by the sparkplug 38. The piston 24 driven by the pressure of the generatedcombustion gas then reciprocates and rotatably drives the crankshaft 26.Thereafter, the combustion gas flows out from the exhaust port 37 asexhaust gas when the exhaust valve 42 is opened. The exhaust gas fromthe exhaust port 37 is flowed through the exhaust pipe 46 a connected tothe connection portion 21 t of the cylinder head 21 to which the outletof the exhaust port 37 is opened and is exhausted to the outside throughthe exhaust device 46. The rotation of the crankshaft 26 isautomatically speed changed according to the rotation speed of theengine by the transmission 15, and transmitted to the rear wheel 10thereby rotatably driving the rear wheel 10 by the internal combustionengine E.

With reference to FIGS. 2 to 5, the cooling device 50 supplies anddischarges cooling water to the water jackets Jb, Jh configured by acylinder block water jacket Jb arranged in the cylinder block 20 so asto surround the cylinder bore 20 b, and a cylinder head water jacket Jharranged in the cylinder head 21 so as to communicate with the cylinderblock water jacket Jb through a communication hole formed in a gasket 49and so as to cover the combustion chamber 35.

The cooling device 50 includes a water pump 51 for pumping out thecooling water to the water jackets Jb, Jh; a radiator 52 through whichthe cooling water of the water jackets Jb, Jh flows; a cooling fan 53for generating cooling wind for promoting heat radiation of the coolingwater flowing through the radiator 52; a shroud 54 for covering thecooling fan 53; a radiator cover 55 for guiding the cooling wind towardsthe radiator core 52 c of the radiator 52; a wind exhaust duct 70 forexhausting cooling wind which is cooling wind passed through theradiator 52 to the atmosphere; a thermostat 56 for communicating andshutting off cooling water between the radiator 52 and the water pump 51so as to control flow and shutting off of the cooling water to theradiator 52 according to the warm-up state of the internal combustionengine E; and a piping group through which the cooling water flows.

The water pump 51 is attached to the right end portion 21 e, which isthe end closer to the radiator 52 in the right direction, of thecylinder head 21. The water pump 51 includes: a body 51 a connected tothe right end portion 21 e; a cover 51 b connected to the body 51 a witha bolt and formed with an intake port portion 51 i and a discharge portportion 51 e; a pump shaft 51 c rotatably supported at the body 51 a andconnected to the axial end portion of the camshaft 40 a; and an impeller51 d connected to the pump shaft 51 c and arranged in a pump chamber 51p formed by the body 51 a and the cover 51 b.

The radiator 52 is arranged spaced apart in the right direction servingas one side in the direction of the rotational axis that is a vehiclewidth direction (left and right direction in the embodiment) withrespect to the crankcase 23. Substantially the entire radiator 52 isarranged at the rear of the cylinder block 20 and the cylinder head 21in the front and rear direction (see FIG. 4), and is arranged at aposition overlapping the crankcase 23 when seen from the right direction(that is when seen from the side, or when seen in the flow-in directionof the cooling wind). The AC generator 31 and the cooling fan 53 arearranged between the chain chamber 44 and the radiator 52 in the rightdirection with respect to the crankcase 23.

The radiator 52 is connected to the right end portion 23 e, which is theend closer to the radiator 52 in the right direction, of the crankcase23 by way of the shroud 54. The radiator 52 includes: an upper tank 52 aserving as an inlet tank formed with an inlet connection portion 52 i tobe connected with an inlet piping 57 for guiding from the cylinder head21 to the radiator 52 high temperature cooling water after flowingthrough both water jackets Jb, Jh and cooling the cylinder block 20 andthe cylinder head 21; a radiator core 52 c including a great number ofheat transfer tubes 52 c 1 to which the cooling water in the upper tank52 a flows; and a lower tank 52 b serving as an outlet tank to which thelow temperature cooling water after radiating in the radiator core 52 cflows from each heat transfer tube 52 c 1 and collected thereat. Thelower tank 52 b is formed with an outlet connection portion 52 e to beconnected with an outlet piping 58 for guiding the cooling water afterheat radiation to the water pump 51 through the thermostat 56.

With reference to FIG. 3, the cooling fan 53 connected to the driveshaft 29 by way of the rotor 31 b of the AC generator 31 is arrangedbetween the rotor 31 b and the radiator core 52 c in the direction ofthe rotational axis. The radial flow cooling fan 53 including a greatnumber of vanes 53 a is arranged to face the radiator core 52 c in thedirection of the rotational axis at the downstream of the radiator core52 c in the wind path formed by the radiator cover 55 and the shroud 54,and generates cooling wind that flows into the radiator core 52 c fromthe upstream by taking in air that has passed through the radiator core52 c.

The shroud 54 is a single member made of synthetic resin including aholding portion 54 a for holding the radiator 52 and a cylindrical coverportion 54 b for covering the outer side in the radial direction of thecooling fan 53. The covering portion 54 b is formed with a wind outletportion 54 e configured by a plurality of slits formed substantiallyparallel in the direction of the rotational axis at an interval in thecircumferential direction of the cooling fan 53, and an exhausted windguiding portion 54 i for guiding the cooling wind to the wind exhaustduct 70 (see FIG. 4). The exhausted wind guiding portion 54 i is formedat the upper portion 54 b 1 of the covering portion 54 b and the windoutlet portion 54 e is formed at the rear portion 54 b 2 of the coveringportion 54 b. The cooling wind that has passed through the radiator core52 c and cooled the radiator core 52 c (hereinafter referred to as“exhausted wind”) is passed through the wind outlet portion 54 e anddischarged to the atmosphere or the outside of the internal combustionengine E, guided by the exhausted wind guiding portion 54 i to be flowedinto the wind exhaust duct 70 and discharged to the atmosphere throughthe wind exhaust duct 70 by the cooling fan 53.

The radiator cover 55 arranged so as to cover the outer periphery of theradiator 52 and face the radiator core 52 c by being connected to theshroud 54 includes a grille 55 a including a latticed current plate. Thegrille 55 a guides the upstream air of the radiator core 52 c, whichflows from the right direction of a side in the vehicle width direction,as cooling wind so as to be directed towards the radiator core 52 c.

With reference to FIG. 1, FIG. 2, FIG. 4, and FIG. 5, the wind exhaustduct 70 forming the wind exhaust path 75 including a wind exhaust inletportion 75 i and a wind exhaust outlet portion 75 e is arrangedextending linearly along the rotational axis Le across the upperportions of both half cases 23 a, 23 b or the upper end portions 23 a 1,23 b 1 in the embodiment, and the upper portions of the case body 16 aand the transmission cover 16 b or the upper end portions 16 a 1, 16 b 1in the embodiment in the power transmission system T arranged on theside opposite to the radiator 52, the cooling fan 53, and the shroud 54with the crankcase 23 in between in the direction of the rotationalaxis. Thus, the power transmission system T is arranged on the leftdirection serving as the other side in the direction of the rotationalaxis with respect to the crankcase 23.

The passage cross section of the wind exhaust duct 70 has a width in theup and down direction reduced compared to the width in the front andrear direction or the direction of the cylinder axis so as to have aflat shape in the up and down direction, and has a substantially wingcross section. The upper wall 70 a of the wind exhaust duct 70 has across sectional shape in which a cross section in the plane orthogonalto the rotational axis Le is an arc shape having the rotational axis Leas the center, and smoothly connects to the crankcase 23 and thetransmission case 16 at the rear portion 70 a 1. Furthermore, the windexhaust duct 70 is at a position lower than the upper most portion 22 hof the head cover 22 (see FIG. 5).

The wind exhaust duct 70 is configured by first and second engine sideduct portions 71, 72 integrally formed with each half body 23 a, 23 b,respectively, and spaced apart from the crank chamber 27 by upper endportions 23 a 1, 23 b 1 immediately above the crank chamber 27, andfirst and second transmission side duct portions 73, 74 integrallyformed with the case body 16 a and the transmission cover 16 b,respectively, and spaced apart from the power transmission chamber 17 byupper end portions 16 a 1, 16 b 1 immediately above the transmissionchamber 17 (see FIG. 3). In the present embodiment, the left half case23 a and the case body 16 a are integrally formed to form a singlemember, and thus the second engine side duct portion 72 and the firsttransmission side duct portion 73 are also integrally formed.

Each duct portion 71, 72, 73, 74 includes partition walls 71 b, 72 b, 73b, 74 b for dividing the wind exhaust path 75 into two in the presentembodiment. Each partition wall 71 b, 72 b, 73 b, 74 b extends along therotational axis Le in each duct portion 71, 72, 73, 74 and forms apartition wall 70 b extending across the entire length of the windexhaust duct 70.

The first engine side duct portion 71 forms a wind exhaust inlet portion75 i opening to the right direction at the wind exhaust guiding portion54 i formed at a position facing the cooling fan 53 at the outer side inthe radial direction of the cooling fan 53, and the exhausted windpushed radially outward by the cooling fan 53 flows in through the windexhaust guiding portion 54 i. The exhausted wind flowed into the firstengine side duct portion 71 sequentially flows through the second engineside duct portion 72 and the first transmission side duct portion 73 inparallel to the rotational axis Le and reaches the second transmissionside duct portion 74, and is exhausted to the atmosphere from the secondtransmission side duct portion 74 forming the wind exhaust outletportion 75 e positioned in the left direction from the transmissioncover 16 b and opened downward. Thus, the wind exhaust duct 70 isarranged across the entire width of the power unit P in the direction ofthe rotational axis.

The thermostat 56 attached to the right end portion 20 e, which is theend closer to the radiator 52 in the right direction, of the cylinderblock 20 includes a housing 56 a connected to the right end portion 20e, and a thermostat valve (not shown) that is operated by a temperaturesensitive element accommodated in the housing 56 a. The housing 56 a isformed with a bypass port portion 56 b to which the cooling water fromthe cylinder head water jacket Jh flows, an inlet port portion 56 i forguiding the cooling water from the radiator 52 into the housing 56 a,and an outlet port portion 56 e for flowing out the cooling water fromthe radiator 52 to the water pump 51.

The thermostat valve allows the cooling water to flow between the bypassport portion 56 b and the outlet port portion 56 e and at the same timeshuts off the flow of cooling water between the inlet port portion 56 iand the outlet port portion 56 e in warm-up of the internal combustionengine E, and allows the cooling water to flow between the inlet portportion 56 i and the outlet port portion 56 e and at the same time shutsoff the flow of cooling water between the bypass port portion 56 b andthe outlet port portion 56 e in completion of warm-up of the internalcombustion engine E.

The inlet piping 57 is connected to the cooling water outlet 61 formedat the right end portion 21 e of the cylinder head 21, and guides thecooling water that has flowed in from the cylinder block water jacket Jbto the cylinder head water jacket Jh and cooled the cylinder head 21. Afixing portion 21 a of the temperature sensor 66 (see FIG. 2) fordetecting the cooling water temperature is arranged in the vicinity ofthe cooling water outlet portion 61.

The inlet piping 57 is configured by a conduit 57 a connected to thecooling water outlet portion 61, a conduit 57 b connected to the inletconnection portion 52 i, and a pipe joint 57 c for connecting theconduits 57 a, 57 b. The inlet piping 57 is formed with a conduit 59 bbranched at the pipe joint 57 c and connected to the bypass port portion56 b, and the bypass piping 59 communicating to the cylinder head waterjacket Jh is configured by the conduit 59 b, the conduit 57 a, and thepipe joint 57 c. The bypass piping 59 guides the cooling water from thecylinder head water jacket Jh to the water pump 51 through thethermostat 56 without flowing into the radiator 52 in warm-up of theinternal combustion engine E.

The outlet piping 58 connected to the intake port portion 51 i forguiding low temperature cooling water from the radiator to the waterpump 51 through the thermostat 56 is configured by a conduit 58 aconnected to the outlet connection portion 52 e and the inlet portportion 56 i, and a conduit 58 b connected to the outlet port portion 56e and the intake port portion 51 i .

A supply pipe 60 connected to the discharge port portion 51 e isconnected to the cooling water inlet portion 62 arranged at the lowerend of the cylinder block 20, and guides the cooling water that hasflowed in from the radiator 52 and discharged from the water pump 51 tothe cylinder block water jacket Jb.

When the internal combustion engine E is operated, the cooling waterpumped out by the water pump 51 flows into the cylinder block waterjacket Jb from the cooling water inlet portion 62 through the supplypipe 60 to cool the cylinder block 20 and then flows into the cylinderhead water jacket Jh to cool the cylinder head 21 by the cooling device50, and thereafter, flows out from the cylinder head water jacket Jh tothe cooling water outlet portion 61, flows into the thermostat 56through the bypass piping 59, and further flows into the water pump 51and force-fed by the impeller 51 d, so that the cooling water circulatesthrough the circulating path in time of warm-up without flowing throughthe radiator 52 thereby promoting warm-up of the internal combustionengine E.

After the completion of warm-up of the internal combustion engine E, thecooling water heat radiated by the radiator 52 to be of low temperatureis pumped by the water pump 51, and the cooling water force-fed by theimpeller 51 d flows into the cylinder block water jacket Jb through thesupply pipe 60 to cool the cylinder block 20 and then flows into thecylinder head water jacket Jh to cool the cylinder head 21, andthereafter, the cooling water flowed out from the cylinder head waterjacket Jh flows into the upper tank 52 a of the radiator 52 through theinlet piping 57 from the cooling water outlet portion 61 to be cooled bythe cooling wind at the radiator core 52 c, and then flows into thelower tank 52 b. The cooling water from the lower tank 52 b passesthrough the outlet piping 58 and flows into the water pump 51 throughthe thermostat 56 and force-fed by the impeller 51 d, so that thecooling water circulates through the circulating path after warm-up andthe cylinder block 20 and the cylinder head 21 are cooled.

The outside air is taken in at the right portion of the power unit P bythe cooling fan 53 rotatably driven by the crankshaft 26 and theradiator core 52 c is cooled by the cooling wind flowing in from thegrille 55 a, whereby heat radiation from the cooling water flowingthrough the radiator core 52 c is promoted. The cooling wind that haspassed through the radiator 52 and cooled the cooling water flows intothe wind exhaust duct 70 through the exhausted wind guiding portion 54 ias exhausted wind, and is discharged downward from the wind exhaustoutlet portion 75 e at the left end of the power unit P through the windexhaust duct 70.

The operation and effect of the embodiment configured as above will nowbe described.

The cooling device 50 of the internal combustion engine E supported bythe body frame F in a swinging manner integrally with the rear wheel 10includes a wind exhaust duct 70 for exhausting the cooling windgenerated by the rotation of the cooling fan 53 and passed through theradiator 52 to the atmosphere, where the wind exhaust duct 70 isarranged at the upper end portions 23 a 1, 23 b 1 in the upper portionof the crankcase 23 and the upper end portions 16 a 1, 16 b 1 in theupper portion of the transmission case 16, whereby limitations relatedto the size of the passage area of the wind exhaust duct 70 are smallcompared to when the wind outlet portion of large passage area is formedin the shroud 54, and the wind volume of the cooling wind that passesthrough the radiator 52 can be increased by increasing the passage areaof the wind exhaust duct 70 since the wind exhaust duct 70 is arrangedusing the upper end portions 23 a 1, 23 b 1 and the upper end portions16 a 1, 16 b 1 even in the motorcycle 1 where enhancement of the coolingperformance of the radiator 52 by traveling wind 52 cannot be expectedtoo much as the radiator 52 is arranged lateral to the crankcase 23serving as the engine main body, thereby enhancing the coolingperformance of the radiator 52, and furthermore, the internal combustionengine E, without enlarging the radiator core 52 c of the radiator 52and the cooling fan 53. Furthermore, the wind volume of the cooling windcan be further increased since the wind outlet portion 54 e is formed inthe shroud 54.

The power transmission system T including the transmission case 16 foraccommodating the transmission 15 is arranged on the side opposite tothe radiator 52 with the crankcase 23 in between in the direction of therotational axis of the crankshaft 26, and the wind exhaust duct 70 isextended along the rotational axis Le of the crankshaft 26 andpositioned at the upper end portions 16 a 1, 16 b 1 of the transmissioncase 16, whereby the wind exhaust duct 70 is extended up to the sideopposite to the radiator 52 with the crankcase 23 in between therebypreventing the exhausted wind exhausted to the atmosphere from flowingin from the grille 55 a and again passing through the radiator 52 whilethe vehicle is stopped, thus enhancing the cooling performance of theradiator 52.

The power unit P including the internal combustion engine E and thepower transmission system T is arranged at the lower portion of thecrankcase 23 and is also supported by the body frame F with the brackets18 a, 18 b positioned at the lower portion with respect to the powertransmission system T, whereby the brackets 18 a, 18 b for supportingthe internal combustion engine E, and furthermore, supporting the powerunit P are not arranged at the upper end portions 23 a 1, 23 b 1 of thecrankcase 23 and at the upper end portions 16 a 1, 16 b 1 of thetransmission case 16 thus increasing the passage area of the windexhaust duct 70 arranged at the upper end portions 23 a 1, 23 b 1 andthe upper end portions 16 a 1, 16 b 1 by such amount and increasing thewind volume of the cooling wind, thereby enhancing the coolingperformance of the radiator 52 and increasing the degree of freedom oflayout of the wind exhaust duct 70.

The passage cross section of the wind exhaust duct 70 has the width inthe up and down direction reduced compared to the width in the front andrear direction or the direction of the cylinder axis so as to have aflat shape in the up and down direction, whereby the crankcase 23 andthe transmission case 16 arranged with the wind exhaust duct 70 aresuppressed from enlarging in the up and down direction. Furthermore, theupper wall 70 a of the wind exhaust duct 70 has a cross sectional shapein which a cross section in the plane orthogonal to the rotational axisLe is an arc shape having the rotational axis Le as the center, andsmoothly connects to the crankcase 23 and the transmission case 16 atthe rear portion 70 a 1, whereby the outer appearance of the power unitP in which the wind exhaust duct 70 is arranged at the upper endportions 23 a 1, 23 b 1 of the crankcase 23 and the upper end portions16 a 1, 16 b 1 of the transmission case 16 improves.

The wind exhaust duct 70 includes the partition wall 70 b for dividingthe wind exhaust path 75. The rigidity of the wind exhaust duct 70 isenhanced since the partition wall 70 b extends along the rotational axisLe, whereby the desired rigidity of the wind exhaust duct 70 is ensuredeven if the passage area of the wind exhaust duct 70 is large.

The second embodiment of the present invention will now be describedwith reference to FIG. 6 to 9. The second embodiment mainly differs fromthe first embodiment in the configuration of the wind exhaust duct, andother configurations are basically the same. The description on the samecomponent thus will be omitted or simplified, and the description willbe made focusing on the different aspect. The same reference numeralsare used, as necessary, for the members same as or members correspondingto the members of the first embodiment.

With reference to FIGS. 6 to 9, the power unit P, and thus, the internalcombustion E and the power transmission system T are supported by thebody frame F in a swinging manner integrally with the rear wheel 10 withthe pair of brackets 18 a, 18 b arranged at the upper portion of thefront end of the power unit P, similar to the first embodiment. Thebracket 18 a is arranged by being integrally molded to the upper portionof the front end of the case body 16 a of the transmission case 16. Thebracket 18 b is arranged by being integrally molded to the upper portionof the front end of the right half case 23 b of the crankcase 23. Thebracket 18 a is integrally molded with the left half case 23 a since thecase body 16 a and the left half case 23 a are integrally molded. Thepair of brackets 18 a, 18 b are supported in a swinging manner by thepivot shaft 13 supported by the pair of support plates 11 respectivelyconnected to the left and right rear frames 4. The power unit P, andthus the internal combustion engine E and the power transmission systemT. Furthermore, the cooling device 50 including the radiator 52 aresupported by the body frame F in a swinging manner in the up and downdirection integrally with the rear wheel 10 by way of the support plate11 and the pivot shaft 13, similar to the first embodiment.

An air intake portion 16 c for taking in air for cooling the belt(similar to belt 15 c of FIG. 1) of the transmission accommodated in thetransmission case 16 is arranged at the front end of the transmissioncover 16 b near the front end of the crankcase 23 when seen from theside (see FIG. 6).

The motorcycle 1 includes fenders 90, 91 that cover the rear wheel 10from the front side towards the rear side and from the outer side in theradial direction with respect to rotational axis Lw of the rear wheel 10(hereinafter simply referred to as “radial direction”). The fenders 90,91 include an outer fender 90 serving as a fixed fender that is attachedand fixed to the body frame F and an inner fender 91 serving as amovable fender that is positioned radially inward (i.e., towardsrotational axis Lw) from the outer fender 90 and that swings withrespect to the body frame F integrally with the power unit P and theinternal combustion engine E. The inner fender 91 is attached to theright half case 23 b at an attachment part 92, is attached to the casebody 16 a by way of a stay 94 serving as a fixed member at an attachmentpart 93, and fixed to the power unit P, that is, the internal combustionengine E.

The outer fender 90 covers the rear wheel 10 from the upper side towardsthe rear side. The inner fender 91 covers the rear wheel 10 from thefront side towards the upper side.

A wind exhaust duct 80 forming a wind exhaust path 85 including a windexhaust inlet portion 85 i and a wind exhaust outlet portion 85 e isarranged across the upper portions of both half cases 23 a, 23 b, thatis, the upper ends 23 a 1, 23 b 2 which are the upper walls of both halfcases 23 a, 23 b in the present embodiment.

The wind exhaust duct 80 arranged between the pair of brackets 18 a, 18b in the left and right direction (which is also the vehicle widthdirection) is a separate component from each half case 23 a, 23 b and isintegrally coupled to the inner fender 91 by being integrally moldedwith the inner fender 91. The wind exhaust duct 80 is arrangedimmediately above the half cases 23 a, 23 b so as to cover the upperface 23 a 5, 23 b 5 of each half case 23 a, 23 b and the rear face 23 a6, 23 b 6 extending downward from the corresponding upper face 23 a 5,23 b 5. The upper face 23 a 5, 23 b 5 and the rear face 23 a 6, 23 b 6form the outer surface of the respective half case 23 a, 23 b.

In this embodiment, the wind exhaust duct 80 is a cover shaped componentthat covers the half cases 23 a, 23 b from the upper side, and forms thewind exhaust path 85 in cooperation with each half case 23 a, 23 b. Theexhausted wind thus contacts each half case 23 a, 23 b and flows throughthe wind exhaust path 85, whereby the crankcase 23 is cooled by theexhausted wind. The wind exhaust duct 80 may be a tubular component sothat only the wind exhaust duct 80 forms the wind exhaust path 85.

With reference to FIG. 7 to 9, the wind exhaust duct 80 is configured byan upstream duct part 81 forming the wind exhaust inlet portion 85 iopening towards the right at the exhausted guiding portion (similar toexhausted wind guiding portion 54 i of the first embodiment) of theshroud 54, a downstream duct part 83 coupled to the fender 91 at thedownstream end 83 a and forming the wind exhaust outlet portion 85 e,and a bent duct part 82 for connecting the upstream duct part 81 and thedownstream duct part 83, thereby forming a bent wind exhaust path 85.

The wind exhaust duct 80 linearly extends towards the left substantiallyparallel to the left and right direction at the upstream duct part 81with the wind exhaust path 85 extending from the wind exhaust inletportion 85 i towards the wind exhaust outlet portion 85 e, bends towardsthe rear at the bent duct part 82, and then linearly extends towards therear at the downstream duct part 83 substantially parallel to the frontand back direction, and thus has an L-shaped part when seen in the upand down direction (i.e., in plan view).

In the present embodiment, the wind exhaust duct 80 is a cover shapedcomponent that covers the crankcase 23 from the upper side and has ashape in lateral cross section of a horseshoe shape with respect to theflow of the exhausted wind, and is opened to each half case 23 a, 23 band towards the lower side. The wind exhaust duct 80 forms the windexhaust path 85 in cooperation with each half case 23 a, 23 b. Theexhausted wind thus contacts each half case 23 a, 23 b and flows throughthe wind exhaust path 85, whereby the crankcase 23 is cooled by theexhausted wind. The downward duct part 83 includes an upper wall 83 cand a pair of side walls 83 d connecting to the upper wall 83 c andlying in the left and right direction.

The wind exhaust duct 80 may be a tubular component so that only thewind exhaust duct 80 forms the wind exhaust path 85.

The wind exhaust outlet portion 85 e has at least one part formed by acoupling portion 83 b (downstream end 83 a in the present embodiment) ina region coupled to the inner fender 91 at the downstream duct part 83.In the present embodiment, the wind exhaust outlet portion 85 e isformed by the coupling portion 83 b to the fender 91 in each side wall83 d, the half cases 23 a, 23 b, and a distal end portion 86 a of ashielding part 86, to be hereinafter described. The wind exhaust outletportion 85 e is an opening formed in the inner fender 91 itself thatopens at a position facing a tread 10 b of a tire 10 a of the rear wheel10 in the radial direction, and arranged at a portion covering the rearwheel 10 from the front or from diagonally above from the front at theinner fender 91.

The wind exhaust outlet portion 85 e opens to an inner space S1, whichis a space formed between the rear wheel 10 and the inner fender 91 inthe radial direction. Therefore, the exhausted wind of the wind exhaustduct 80 is exhausted to the inner space S1 formed radially inward withrespect to the inner fender 91 using the wind exhaust outlet portion 85e or through the wind exhaust outlet portion 85 e. The exhausted wind isexhausted from the wind exhaust outlet portion 85 e in a direction of arotating direction R at a region 10 c (region 10 c is part of the tread10 b of the tire 10 a) closest to the wind exhaust outlet portion 85 ein the rear wheel 10 and diagonally downward towards the rear. In FIG.9, the outline of the flow of the exhausted wind is shown with anoutlined arrow.

The direction of the rotating direction R means that the exhausted windincludes flow components in the direction same as the direction of therim speed of the rear wheel 10 at the region 10 c. The rotatingdirection R of the rear wheel 10 is the rotating direction of when themotorcycle 1 moves forward.

Most of the wind exhaust outlet portion 85 e is positioned below theupper faces 23 a 5, 23 b 5, 23 a 6, 23 b 6 of the crankcase and theupper face 16 d of the transmission case 16 (see also FIG. 6), and ispositioned in a space having the front side shielded by the crank case23 and the left direction shielded by the transmission case 16, andfurthermore, the exhausted wind exhausted from the wind exhaust outletportion 85 e is reliably prevented from being taken in from the airintake portion 16 c of the transmission case 16 since the exhausted windis exhausted downward from the wind exhaust outlet portion 85 e.

The shielding part 86 is arranged on the downstream duct part 83 tosuppress foreign materials taken up by the rear wheel 10 or foreignmaterials such as small rocks, dirt, and dust that were attached to thetread 10 b and scattered by centrifugal force from entering inside thewind exhaust duct 80 or the wind exhaust path 85. The shielding part 86prevents the foreign materials from being scattered over the shieldingpart 86, and thus is a portion that also has the function of the fender91, whereby the wind exhaust duct 80 arranged with the shielding part 86also serves as the fender 91.

The shielding part 86 is a canopy part or canopy shaped wall extendingin a direction of the rotating direction R at the region 10 c ordiagonally downward at the rear from the upper wall 83 c in the couplingportion 83 b or in the vicinity of the coupling portion 83 b.

The shielding part 86 is integrally coupled and arranged with thedownstream duct part 83 by being integrally molded with the downstreamduct part 83. Furthermore, the shielding part 86 is connected to thesidewalls 83 d and is arranged across the entire width of the downstreamduct part 83 or the wind exhaust path 85 in the left and rightdirection. The wind exhaust outlet portion 85 e is formed below thedistal end portion 86 a of the shielding part 86.

The shielding part 86 extends downward along the rear faces 23 a 6, 23 b6 of the rear walls 23 a 2, 23 b 2 of the respective half cases 23 a, 23b (see FIG. 9). Thus, the exhausted wind that flows in a substantiallyhorizontal direction between the upper ends 23 a 1, 23 b 1 of each halfcase 23 a, 23 b and the wind exhaust duct 80 is deflected downward bythe shielding part 86, and the exhausted wind that has been deflectedflows out from the wind exhaust outlet portion 85 e, and flows along therear face 23 a 6, 23 b 6 of each half case 23 a, 23 b. The shieldingpart 86 thus also acts a deflecting part for deflecting the exhaustedwind towards the wind exhaust outlet portion 85 e.

The rear wall 23 a 2, 23 b 2 of each half cases 23 a, 23 b is at aposition facing the tread 10 b in the radial direction and in the frontand back direction, and serves as a fender continuing from the innerfender 91 in the rotating direction R. The exhausted wind exhausted fromthe wind exhaust outlet portion 85 e in the direction of the rotatingdirection R at the region 10 c mostly flows through the inner space S1and into an outer space S2 serving as a space formed between the rearwalls 23 a 2, 23 b 2 and the rear wheel 10 in the radial direction andin the front and back direction. Airflow A in the direction of therotating direction generated by the rotation of the rear wheel 10 existsin the outer space S2 due to flow resistance of air.

When the motorcycle 1 travels, the exhausted wind, which is the coolingwind passed through the radiator 52 and cooled the cooling water, flowsinto the wind exhaust duct 80 from the shroud 54, through the windexhaust duct 80, and then exhausted in the direction of the rotatingdirection R at the region 10 c in the inner space S1 and also downwardfrom the wind exhaust outlet portion 85 e at the rear of the crankcase23, and furthermore, flows downward through the outer space S2 with theair flow A generated by the rotation of the rear wheel 10.

According to the second embodiment, in the motorcycle 1 mounted with theinternal combustion engine E equipped with the cooling device 50 havingthe radiator 52 arranged lateral to the crankcase 32, the internalcombustion engine E is supported by the body frame F in a swingingmanner integrally with the rear wheel 10, the cooling device 50 includesthe wind exhaust duct 80 for exhausting the exhausted wind, which is thecooling wind passed through the radiator 52, to the atmosphere from thewind exhaust outlet portion 85 e, and the wind exhaust duct 80 isarranged at the upper ends 23 a 1, 23 b 1 of the crankcase 23 so thatthe motorcycle 1 is mounted with the internal combustion E, where thefollowing effects are obtained in addition to the effects similar to thefirst embodiment since the wind exhaust duct 80 is arranged using theupper ends 23 a 1, 23 b 1 of the crankcase 23 in the motorcycle 1 whereenhancement in the cooling performance of the radiator 52 by thetraveling wind cannot be expected too much since the radiator 52 isarranged lateral to the crankcase 23.

The wind exhaust duct 80 is coupled with the inner fender 91 and thewind exhaust outlet portion 85 e is formed by the coupling portion 83 bto the inner fender 91 of the wind exhaust duct 80, so that theexhausted wind of the wind exhaust duct 80 is exhausted to the innerspace S1 through the wind exhaust outlet portion 85 e or the openingformed in the inner fender 91, whereby the exhausted wind from the windexhaust outlet portion 85 e is prevented from hitting the fender 91 thusinhibiting the exhaust of the exhausted wind, and furthermore, the windexhaust duct 80 can be miniaturized and compact arrangement can beachieved since the wind exhaust duct 80 does not need to be arrangedavoiding the inner fender 91. The wind exhaust duct 80 is integrallymolded with the inner fender 91 thereby reducing the number ofcomponents.

The wind exhaust outlet portion 85 e opens to the position facing thetread 10 b of the rear wheel 10 in the radial direction, and the windexhaust duct 80 or the inner fender 91 is arranged with the shieldingpart 86 for suppressing foreign materials taken up by the rear wheel 10or foreign materials that were attached to the tread 10 b and scatteredby centrifugal force from entering into the wind exhaust duct 80,whereby exhaust of the exhausted wind from the wind exhaust outletportion 85 e is prevented or suppressed from being inhibited by foreignmaterials by the shielding part 86, and thus the flow of the exhaustedwind in the wind exhaust duct 80 including the wind exhaust outletportion 85 e becomes smooth, which contributes to enhancing the coolingperformance of the radiator 52.

The shielding part 86 extends along the rear faces 23 a 6, 23 b 6 or theouter surfaces of the crankcase 23, and thus the exhausted windexhausted from the wind exhaust duct 80 flows along the rear faces 23 a6, 23 b 6, whereby the contacting range of the rear faces 23 a 6, 23 b 6and the exhausted wind increases and the cooling effect of the crankcase23 by the exhausted wind enhances.

Since the air flow A in the direction substantially the same as theexhausting direction of the exhausted wind is generated by the rotationof the rear wheel 10 in the inner space S1 or the outer space S2 whenthe exhausted wind is exhausted from the wind exhaust outlet portion 85e in the direction of the rotating direction R at the region 10 cclosest to the wind exhaust outlet portion 85 e in the rear wheel 10 tothe inner space S1 between the rear wheel 10 and the inner fender 91 orthe outer space S2 between the rear wheel 10 and the crankcase, theexhaust of the exhausted wind from the wind exhaust outlet portion 85 eis promoted by using the air flow A, and thus the wind volume of thecooling wind that passes through the radiator 52 increases and thecooling performance of the radiator 52 enhances.

The third embodiment of the present invention will now be described withreference to FIG. 10. The third embodiment differs from the secondembodiment regarding the fender, but other configurations are basicallythe same. The description on the same component thus will be omitted orsimplified, and the description will be made focusing on the differentaspect. The same reference numerals are used, as necessary, for themembers same as or members corresponding to the members of the secondembodiment.

The motorcycle 10 includes one fender 96 that covers the rear wheel 10from the front side towards the rear side and from the outer side in theradial direction. The fender 96 is a movable fender that can swing withrespect to the body frame F integrally with the power unit P and theinternal combustion engine E, and is attached and fixed to the crankcaseand the transmission case 16 by way of a stay (not shown) serving as afixing member. The fender 96 covers at least the rear wheel 10 from thefront or from diagonally above from the front, similar to the innerfender 91 of the second embodiment.

Similar to the second embodiment, the wind exhaust duct 80 is a separatecomponent from the crankcase 23, and is coupled with the fender 96 bybeing integrally molded with the fender 96. The shielding part 86 isintegrally molded with the wind exhaust duct 80.

According to the third embodiment, effects similar to the secondembodiment are obtained.

An embodiment in which the configuration of one part of the embodimentdescribed above is modified will be described below regarding themodified configuration.

In the first embodiment, the wind exhaust duct 70 may be a separatecomponent from the crankcase 23.

The wind outlet portion 54 e does not need to be formed at the shroud54.

An electrically operated motor may rotatably drive the cooling fan. Theinternal combustion engine may be a multi-cylinder internal combustionengine including a cylinder block configured by a plurality ofintegrally formed cylinders.

The internal combustion engine may be arranged in the internalcombustion engine used in machines other than in vehicles such as astationary type internal combustion engine. The internal combustionengine and the transmission may be supported while being fixed to thebody frame.

The shielding part 86 may be arranged on the fenders 91, 96. Theshielding part 86 may be a separate component from the fenders 91, 96 orthe wind exhaust duct 80. The shielding part 86 may be arranged in theleft and right direction with a spacing, or may be arranged at one partof the width of the downstream duct part 83 in the left and rightdirection.

The wind exhaust duct 80 and the fenders 91, 96 may be separatecomponents, and integrally coupled by coupling means such as screw,welding, adhesive, etc. If the wind exhaust duct 80 and the fenders 91,96 are separate components, they are arranged in a non-coupled state, sothat the exhausted wind exhausted from the wind exhaust outlet portion85 e flows through the openings formed in the fender 91, 96 and into theinner space S1 of the fender 91.

Using the opening formed in the fender 91, 96, the downstream duct part83 may be passed through the opening and coupled to the fenders 91, 69at the region on the upstream side from the downstream end 83 a orarranged with respect to the fenders 91, 96 so that the downstream end83 a of the downstream duct part 83 is positioned in the inner space S1.

When the wind exhaust outlet portion 85 e opens to substantiallyimmediately below, the shielding part 86 does not need to be arrangeddepending on the form of the wind exhaust outlet portion 85 e.

Moreover, most of or all of the exhausted wind from the wind exhaustoutlet portion 85 e may be directly exhausted to the outer space S2without passing through the internal space S1 depending on thepositional relationship of the wind exhaust duct 80 and the fenders 91,96. The invention being thus described, it will be obvious that the samemay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. An internal combustion engine comprising: an engine main bodyconfigured by a crankcase; and a cooling device including a radiatorarranged lateral to the engine main body, said cooling device includinga wind exhaust duct for exhausting exhausted wind, which is cooling windpassed through the radiator, to an atmosphere, wherein the wind exhaustduct is arranged on an upper portion of the crankcase.
 2. The internalcombustion engine according to claim 1, wherein a power transmissionsystem including a transmission case for accommodating a transmission isarranged on the side opposite to the radiator with the crankcase inbetween in a direction of a rotational axis of a crankshaft supported bythe crankcase, and the wind exhaust duct extends along the rotationalaxis of the crankshaft and is positioned on the upper portion of thetransmission case.
 3. The internal combustion engine according to claim2, wherein the internal combustion engine is supported by a body frameat supporting parts arranged at a lower portion of the crankcase.
 4. Theinternal combustion engine according to claim 1, wherein the internalcombustion engine is supported by a body frame at supporting partsarranged at a lower portion of the crankcase.
 5. A vehicle with wheels,the vehicle comprising: an internal combustion engine mounted thereon,the internal combustion engine including an engine main body configuredby a crankcase, and a cooling device, the cooling device including: aradiator arranged lateral to the engine main body; a wind exhaust ductfor exhausting exhausted wind, which is cooling wind passed through theradiator, from a wind exhaust outlet portion to an atmosphere, whereinthe wind exhaust duct is arranged on an upper portion of the crankcase.6. The vehicle according to claim 5, further comprising: a fender forcovering the wheel from an outer side in a radial direction having arotational axis of the wheel as a center, wherein the exhausted wind isexhausted to a space formed between the wheel on an inner side in theradial direction and the fender using an opening formed in the fender.7. The vehicle according to claim 6, wherein the wind exhaust outletportion opens at a position facing a tread of the wheel in the radialdirection, and a shielding part for suppressing foreign materials, thatare taken up by the wheel or foreign materials that are attached to thetread and scattered by a centrifugal force, from entering inside thewind exhaust duct, the shielding part being arranged in the wind exhaustduct or the fender.
 8. The vehicle according to claim 7, wherein theshielding part extends along an outer surface of the crankcase.
 9. Thevehicle according to claim 5, further comprising: a fender for coveringthe wheel from an outer side in a radial direction having a rotationalaxis of the wheel as a center, wherein the wind exhaust duct is coupledwith the fender, and the wind exhaust outlet portion is formed by acoupling portion that couples the wind exhaust duct to the fender. 10.The vehicle according to claim 6, wherein the exhausted wind isexhausted from the wind exhaust outlet portion to a space formed betweenthe wheel and the fender or to a space formed between the wheel and thecrankcase in a rotating direction at a region closest to the windexhaust outlet portion in the wheel.
 11. The vehicle according to claim9, wherein the exhausted wind is exhausted from the wind exhaust outletportion to a space formed between the wheel and the fender or to a spaceformed between the wheel and the crankcase in a rotating direction at aregion closest to the wind exhaust outlet portion in the wheel.
 12. Thevehicle according to claim 5, wherein the wind exhaust outlet portionopens at a position facing a tread of the wheel in the radial direction,and a shielding part for suppressing foreign materials, that are takenup by the wheel or foreign materials that are attached to the tread andscattered by a centrifugal force, from entering inside the wind exhaustduct, the shielding part being arranged in the wind exhaust duct or thefender.
 13. The vehicle according to claim 12, wherein the shieldingpart extends along an outer surface of the crankcase.
 14. The vehicleaccording to claim 12, wherein the exhausted wind is exhausted from thewind exhaust outlet portion to a space formed between the wheel and thefender or to a space formed between the wheel and the crankcase in arotating direction at a region closest to the wind exhaust outletportion in the wheel.
 15. The vehicle according to claim 5, wherein theexhausted wind is exhausted from the wind exhaust outlet portion to aspace formed between the wheel and the fender or to a space formedbetween the wheel and the crankcase in a rotating direction at a regionclosest to the wind exhaust outlet portion in the wheel.